Printing stencil



June 19, 1951 n-z 2,557,352

PRINTING STENCIL Filed April 19, 1947 m l v I O t\\ 0 I o 1 I N oINVENTOR.

4 GEORGES KANITZ BY J M Patented June 19, 1951 UNITED STATES PATENTOFFICE PRINTING STENCIL Georges Kanitz, Caracas, Venezuela ApplicationApril 19, 1947, Serial N0. 742,615

6 Claims. (01. 101-1282) This invention relates to new and improvedprinting stencils and has particular relation to new and improvedstencils adapted to be used in the so-called screen process and to amethod of preparing such stencils.

The main object of my present invention is to provide a stencil for thescreen process, which shows a true and exact reproduction of the designto be printed and can be easily and conveniently produced.

Another object of my present invention is to provide a stencil forscreen process-printing by copying the design directly to the stencillayer without the disadvantage of the so-called mesh-marks.

A further object of this invention is to produce a stencil for screenprocess-printing by first providing the screen with a suitable layerwhich is not sensitive to light, applying the design to be printeddirectly to this layer which is subsequent- 1y rendered sensitive tolight and then insoluble by exposure to light but only in those portionsof the same which are not covered by the design, whereupon the solubleportions of said layer, which are covered by the design and the designproper are removed by dissolution of the soluble portions of the stencillayer and the stencil is ready for use.

Other objects and theadvantages of the invention will be apparent fromthe following specification and claims and the appended drawings whichillustrate, by way of example, some preferred embodiments of theinvention, and in which Figure 1 illustrates diagrammatically in topview a stencil embodying the present invention;

Figure 2 is a sectional view along line 2-2 of Figure l; I

Figure 3 illustrates a part of Figure 2 on an enlarged scale beforedeveloping, and Figure 4 is a view similar to that of Figure 3, afterdeveloping.

. Referring now to the drawings in detail, I is a square frame, whichmay consist of wood or metal, and to which a silk screen 2 of thecustomary type is applied by stretching in the usual manner. 3 denotes adesign, and 4 denotes the material of the stencil before, and 5, after,the developing step.

In carrying out my invention, the solution of a suitable transparent,colloid material, for example an aqueous solution of glue or gelatine isapplied to the screen in order to fill the holes of the screen and forma layer of about 0.3 to 0.5 mm. thickness. The coated screen is dried ata temperature of, for example, 15 to 25 0., and is then brought incontact with the original design to be reproduced and a reproduction isproduced on the surface of the dried colloid layer by painting ordrawing, as indicated in Figures 1 and 2. The design may be of any type,i. e. it may, for example, consist of printed types or a drawing or thelike. In preparing the design to be reproduced on the stencil layer, Iprefer the use of inks, pigments or drawing crayons or the like, whichare impermeable to light. After the said reproduction on the stencillayer has been made and dried, said layer is treated with a hardening orsensitizing solution, for example an aqueous 24% solution of ammoniumbichromate and then dried, in order to render the stencil layersubstantially uniformly sensitive to light. If a sensitizing solutionhas been used, the surface of the stencil layer, which carries thereproduced design, is now exposed to a strong light source and aftersufiicient exposure, developed with warm water. During this developing,those portions of the stencil which are covered by the design and,therefore, have not been affected by the exposure to light, aredissolved, and the drawing adhering to these portions, is also removedfrom the stencil, thus leaving screen holes forming a registeringdesign, open as indicated in Fig. 4. In contrast to this, those portionsof the stencil which were not protected from light by the design andbecame hardened and insoluble by the exposure to light are not removedby water. They adhere to the screen and keep the holes thereof sealed.Thus, after developing and drying, the stencil is ready for use.

According to a modification of my invention, reproduction of the designto be printed may be produced on the stencil layer by means of inks orlacquers or the like, which are permeable to light but impermeable tothe sensitizing solution. After the reproduction of the design to beprinted on a surface of the stencil layer by means of an ink or othermaterial of the before-mentioned type, the surface bearing thereproduced design.

is treated with a sensitizing solution, and, after drawing, said surfaceis exposed to light and then developed with warm water. Owing to thefact that the ink or the like used in reproducing the design isimpermeable to the sensitizing solution,

the portions of the stencil layer covered by the design are notsensitized and not affected by the exposure. These portions and thedesign covering them, are, therefore, removed by the developing step.The developed stencil is dried and is, then ready for printing.

According to another embodiment of my invention, developing of thestencil layer is effected by means of a solution which is capable ofhardening and rendering substantially insoluble or diflicultly solublethe material of the stencil layer. In using such a hardening solution,the design is applied in a manner substantially identical to thatdescribed above, but by means of an ink or the like which is impermeableto said hardening solution. After application of the design to thestencil layer, the surface of the latter, which carries the design, istreated with a suitable hardening solution and then permitted to dry. Inthis trea ment, those portions of the stencil layer which are permeatedby the solution become insoluble or difficultly soluble. After drying,those parts of the stencil layer which have been protected from thehardening solution by the impermeable design are dissolved by means of asolvent, for example, moderately warm water, and are thus removedtogether with the design.

According to my invention the screen is completely filled with thestencil material prior to the reproduction of the design on it. Iprepare the reproduction on a substantially smooth surface and obtainsharp contour lines substantially without any mesh-marks. Furthermore,in contrast to prior processes, I can use stencil layers of considerablethickness, which completely fill the holes of the screen, or may evenform a thicker the stencil layer prior to sensitizing or harden- 1'1:

ing, the lines of the design are in intimate contact with the stencillayer. This results in true and exact reproductions and greatlyfacilitates true reproduction of fine details.

It will be apparent that my present invention is not limited to thespecific details and steps disclosed and may be carried out with variousmodifications. For example, instead of the above described solution ofglue or gelatine, other colloid solutions which are adapted to form atransparent layer substantially without the formation of bubbles and canbe sensitized to light, and other sensitizing solutions and varioushardening solutions may be used. For example, layers of fish glue orgelatin may be hardened and rendered insoluble by the action of a 56%aqueous solution of chrome alum, or a aqueous formaldehyde solution, oran aqueous solution containing about 40% formaldehyde and about 5%phenol. As further examples of stencil materials, shellac, collodium,fish glue and transparent synthetic plastics, and as examples of othersensitizing solutions, other compounds of chromium, such as potassiumbichromate may be mentioned. These and other modifications may be madeWithout departing from the spirit and scope of the invention as definedin the appended claims.

The term design is used in the present specification and claims todenote the letters, words, drawings or the like to be printed.

What I claim is:

1. A process for preparing stencils for screen printing, said processcomprising providing a stretched screen with a soluble stencil layerinsensitive to light, applying a design to be printed directly to thesurface of said layer, rendering those portions of the layer, which arenot covered by the design, insoluble by sensitizing and exposure tolight, and removing the portions of the layer covered by the design andsaid design by dissolving these portions of the layer.

2. A process for preparing stencils for screen printing, said processcomprising providing a stretched screen with a soluble stencil layerinsensitive to light, applying a design to be printed directly to thesurface of said layer by means of a painting or drawing materialimpermeable to light, rendering those portions of the layer which arenot covered by the design insoluble by sensitizing said layer andexposing to light the surface carrying the design, and thereafterremoving the portions of the layer covered by the design and said designby dissolving these portions of the layer.

3. A process for preparing stencils for screen printing, said processcomprising providing a stretched screen with a soluble stencil layerinsensitive to light, applying a design to be printed directly to thesurface of said layer by means of a printing or drawing material whichis impermeable to sensitizing solutions, rendering those portions of thelayer which are not covered by the design sensitive to light by treatingthe surface of the layer carrying the design with a sensitizing solutionand then rendering those portions of the layer which are not covered bythe design insoluble by exposure to light, and removing the portions ofthe layer covered by the design and said design by dissolving theseportions of the layer.

4. A process as claimed in claim 2, in which the stencil layer consistsof a dried solution of glue and sensitizing is effected by means of asolution of ammonium bichromate.

5. A process as claimed in claim 3, in which the stencil layer consistsof a dried solution of glue and sensitizing is effected by means of asolution of ammonium bichromate.

6. A product adapted to be used in the preparation of stencils forscreen printing, said product comprising a screen and a stencil layerapplied directly to said screen, said layer consisting of portionsregistering with the design to be printed, which are notlight-sensitized, and residual portions which are light-sensitized.

GEORGES KANITZ.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date Re. 8,853 Zuccato Aug. 12, 1879485,602 Bell Nov. 8, 1892 1,327,931 Waters Jan. 13, 1920 2,064,764Playford Dec. 15, 1936

1. A PROCESS FOR PREPARING STENCILS FOR SCREEN PRINTING, SAID PROCESS COMPRISING PROVIDING A STRETCHED SCREEN WITH A SOLUBLE STENCIL LAYER INSENTITIVE TO LIGTH, APPLYING A DESIGN TO BE PRINTED DIRECTLY TO THE SURFACE OF SAID LAYER, RENDERING THOSE PORTIONS OF THE LAYER, WHICH ARE NOT COVERED BY THE DESIGN, INSOLUBLE BY SENSITIZING AND EXPOSURE TO LIGHT, AND REMOVING THE PORTIONS OF THE LAYER COVERED BY THE DESIGN AND SAID DESIGN BY DISSOLVING THESE PORTIONS OF THE LAYER. 